1. Field of the Invention
The present invention relates to a multi-screen display apparatus that displays an image on a multi-screen constituted by a plurality of screens and a luminance control method.
2. Description of the Background Art
In recent years, in a projection-type image display apparatus, light sources utilizing light emitting diodes (LED (Light Emitting Diodes)) have been used in place of conventional lamp light sources. In particular, in a display apparatus of DLP (registered trade mark) (Digital Light Processing) system that uses DMD's (Digital Micromirror Devices), LED's that emit red light, LED's that emit green light and LED's that emit blue light are used. In the display apparatus of the DLP (registered trade mark) system, these LED's of three colors are lit up on in a time sharing manner.
As the projection-type image display apparatus utilizing LED's as light sources, those using LED arrays constituted by a plurality of LED's have been proposed in order to improve luminance of light sources. In the following description, the LED array that emits red light is referred to also as an R-LED array. Moreover, the LED array that emits green light is referred to also as a G-LED array. In the following description, the LED array that emits blue light is referred to also as a B-LED array.
In these projection-type image display apparatuses, a driving circuit is installed for each of LED's forming an LED array or for each group of a plurality of sets of LED's. More specifically, with respect to the former, for example, each R-LED array includes six LED's. In the six LED's, six driving circuits are respectively installed. With respect to the latter, for example, a structure is proposed in which a driving circuit is installed for each of three sets of LED groups. Each of the LED groups is constituted by, for example, two LED's.
Moreover, in recent years, also in a multi-screen display apparatus that is constituted by a plurality of projection-type image display apparatuses and displays an image on a multi-screen including a plurality of screens, those using LED's as light sources respectively for RGB have been proposed. The multi-screen display apparatus includes a projection-type image display apparatus that displays an image on a screen by projecting an image from the rear face side of the screen.
As the image display apparatus using a plurality of LED's, those utilizing a technique for controlling the quantity of light emission of the light source by controlling the current value of an electric current to be supplied to each LED has been proposed (for example, see Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-185924).
In the multi-screen display apparatus, however, the following problems have been raised.
For example, in the case where one of LED's inside the R-LED array has a failure with the result that the corresponding LED becomes incapable of being lit up, the driving circuit with the failed LED stops the driving operation of the LED. In this case, the image projected on the screen has a reduction in luminance of red color. Consequently, the chromaticity of an image displayed on the multi-screen is also changed.
In particular, in the case of the multi-screen display apparatus constituted by a plurality of image display apparatuses, due to a change of luminance or the like of a certain image display apparatus, homogeneity in luminance among the respective screens on the multi-screen is impaired.